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Resting Energy Expenditure and Cold-induced Thermogenesis in Patients With Overt Hyperthyroidism
Claudia I Maushart1, Jaël R Senn1, Rahel C Loeliger1
1Department of Endocrinology, Diabetes and Metabolism, University Hospital Basel, University of Basel, Petersgraben 4, CH-4031 Basel, Switzerland.
The Journal of Clinical Endocrinology and Metabolism
|September 27, 2021
Summary
Hyperthyroidism does not increase cold-induced thermogenesis (CIT), despite its crucial role in adapting to cold. Resting energy expenditure (REE) significantly decreases as thyroid hormone levels normalize.
Area of Science:
- Endocrinology
- Metabolism
- Thermogenesis
Background:
- Thyroid hormone (TH) plays a vital role in the human body's adaptation to cold environments.
- Understanding how thyroid dysfunction, specifically hyperthyroidism, affects energy expenditure and thermogenesis is crucial for metabolic health.
Purpose of the Study:
- To investigate the impact of hyperthyroidism on resting energy expenditure (REE).
- To evaluate the effect of hyperthyroidism on cold-induced thermogenesis (CIT).
- To assess changes in body composition and weight in hyperthyroid patients.
Main Methods:
- A prospective cohort study involving 18 patients with overt hyperthyroidism.
- Measurements of REE were taken during hyperthyroidism, after achieving euthyroid levels, and 3 months post-normalization.
- CIT was assessed by measuring energy expenditure (EE) before and after cold exposure; body composition was analyzed using dual X-ray absorptiometry.
Main Results:
- Resting energy expenditure (REE) corrected for lean body mass (LBM) significantly decreased by 21% as patients transitioned from hyperthyroid to euthyroid states.
- Free thyroxine (fT4) and free triiodothyronine (fT3) levels were significant predictors of REE.
- Cold-induced thermogenesis (CIT) did not show a significant change between the hyperthyroid and euthyroid states; body weight and composition remained unaffected.
Conclusions:
- Overt hyperthyroidism does not lead to an increase in cold-induced thermogenesis (CIT).
- Resting energy expenditure (REE) is significantly reduced upon normalization of thyroid hormone levels.
- Changes in body weight and composition are not directly influenced by REE or CIT during hyperthyroidism.
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